[Feature resquest] Blend mode

[Pascal-Pouvereau]

Could Olive have a way to manage blendmodes (maybe in the Opacity filter)?

Most useful
prev = previous image
src = current block image

• Normal = src
• Multiply = prev * src]
• Multiply ×2 = prev * src * 2
• Screen = 1 - (1 - prev) * (1 - src)
• Additive = prev + src

More formulas
https://en.wikipedia.org/wiki/Blend_modes
https://www.deepskycolors.com/archivo/2010/04/21/formulas-for-Photoshop-blending-modes.html

[sobotka]

This doesn't work.

The assumption that all values are closed domain tristimulus, such as with the screen mode, does not hold on open domain mixing, where the bounds are infinite.